hx711

[Ken] keeps his bees remotely and can’t check on them as often as he might like to. He wanted some way of knowing when they were out of space, because that slows down their nectar collection. He knew he could do this by remotely tracking the weight and internal temperature of the hives.

His first prototype revolved around a postal scale that couldn’t be turned off between readings. This meant that he needed a bigger solar panel and battery than originally intended. For about a week, the hives were sending data to Thingspeak through an Arduino Fio over XBee.

The current iteration measures the load cells with an HX711 24-bit ADC. This sends the scale data to an Apitronics Bee unit, which adds in temperature data from the hives and sends everything to an Apitronics Hive. [Ken] will also stream it to a cloud service so he can monitor them in real-time. [Ken] wants to see as much data as possible and contribute to NASA’s HoneyBeeNet program, so he has a second Bee unit set up to handle a nearby Apitronics weather station.

How can you not be interested in a project that uses load cells, Bluetooth, a Raspberry Pi, and Twitter. Even for those of our readers without a cat, [Scott’s] tweeting litter box is worth the read.

Each aspect of this project can be re-purposed for almost any application. The inexpensive load cells, which available from eBay and other retailers, is used to sense when a cat is inside the litter box. Typically sensors like the load cell (that contain a strain gauge) this use a Wheatstone bridge, which is very important for maximizing the sensitivity of resistive sensor. The output then goes to a HX711, which is an ADC specifically built for load cells. A simple alternative would be using an instrumentation amplifier and the built-in ADC of the Arduino. Now, the magic happens. The weight reading is transmitted via an HC-06 Bluetooth module to a Raspberry Pi. Using a simple Perl script, the excreted weight, duration, and the cat’s resulting body weight is then tweeted!

Very nice work! This is a well thought out project that we could see being expanded to recognize the difference between multiple cats (or any other animal that goes inside).